The development of high pressure hydraulic devices such as water jet cutting and blast cleaning devices has led to equipment intended for operating at fluid pressures in excess of 40,000 psig. Unique problems are encountered devising reliable hydraulic equipment capable of operating at such high pressures. For example, it may be desired to regulate the pump discharge pressure to a substantially constant yet high pressure value regardless of the rate of flow from the pump. It may also be desired to provide several on/off-jetting guns each fluidly connected to a common pump discharge line, with a pressure regulator maintaining the system at a high discharge pressure which is at or below a substantially constant value, so that each gun may be independently operated from the same fluid source.
High fluid operating pressures require that the system components be mechanically sound to withstand the high pressures, but also be sufficiently simple for both cost effective manufacture and easy replacement of those parts which are subject to high rates of erosion and wear due to the high fluid pressure and flow characteristics. A high pressure regulator or regulating valve that is both reliable and relatively simple is difficult to construct because of the high biasing forces that must be applied to bias the valve member in a closed or controlled position. Additionally, the valve and seat of the regulator must be adapted to operate satisfactorily over extended periods of time yet be mechanically cost effective to manufacture and easy to replace. These parameters are addressed by the prior art to a limited extent, but the prior art has not solved these problems in a satisfactory manner.
U.S. Pat. No. 4,620,562 to Pacht discloses a high pressure regulating valve particularly suited for replacement of component parts. The regulating valve includes a closure member with an integral control piston and a conical seating surface cooperable with a complimentary surface on a seat member. The valve closure member is biased in the closed position by an actuating mechanism which includes a pressure gas control piston and cylinder arrangement utilizing a flexible diaphragm for sealing the actuator pressure chamber. The cross-sectional area of the control piston is large enough to minimize the differences in cross-sectional areas on the closure member exposed to pressure fluid between the valve closed and valve open positions, resulting in a reduced variation between the pressure required to open the regulator valve (regulator opening pressure) and the pressure required to maintain the regulator in its normal operating position with the valve at least partially open (regulator operating pressure).
Use of a regulator manufactured in accord with the '562 patent confirms that the area of engagement between the surface areas of the closure member and the seating member is nominal, leading to early wear and fatigue. Moreover, the relative difference between the cross-sectional area of the control piston and the cross-sectional area of the outlet passage results in a reduced yet undesirable variation between the regulator opening pressure and the regulator operating pressure.
The problems encountered by the '562 patent are also found in the regulators disclosed in U.S. Pat. No. 3,217,742 to Merrill and U.S. Pat. No. 2,750,957 to Tavola. For example, the '957 Patent to Tavola discloses an injection valve having a stem with a conical end that cooperates with a seat in an injection nozzle, wherein the area of engagement between the surface areas of the stem conical end and the seat is relatively low, leading to high wear.
A need exists in the prior art to minimize the variance between the valve opening pressure and the valve operating pressure, while maintaining valve integrity and resistance to erosion and wear.